This specification relates to sharing presence data among users of a web-based document collaboration system. In conventional systems, a client device can share information about itself with a server and/or with peer client devices. The shared information can be requested by the server or by the peer client devices, or the shared information may be sent without solicitation from the server or the peer devices. The shared information can indicate, for example, whether the client device is coupled to a particular communication network, what information the client device is displaying, and/or what actions the client device is taking. For example, a server of an instant messaging service can broadcast information to users of the instant messaging service to indicate that a particular user is logged on for instant messaging. As another example, a client device can send data to a server indicating that the client device is logged on to a particular web site, and the server can then distribute the received data to other client devices, informing the other client devices that the first client device is logged on to the web site. The data distributed to the other client devices can also indicate that the client device is viewing a particular item or web page within the web site.